So I have ordered a new rebuild kit from Hessler which arrived yesterday.Copper seats in my carbs were both a bit loose, new ones fit firmly. Once the float body was out, I couldn't fit it back anymore because of the o-ring was not entering in its seat anymore, like it has become bigger...well replaced the o-ring with the one in the kit and it was back in. I have adjusted float level to "parallel" lines and then made the wet test, but fuel in transparent pipes from the bowls doesn't reach the edge of the bowls but it is few mm lower. I guess I need to readjust float height?In the new kit there are 3 more o-rings, not sure to know where they all go...can you help?

Done again the test and now fuel level seems correct. I have reassemble everything, including a new airbox (mine had a hole in the bottom) and seems to run fine, but I did just a test in the garage, couple of minutes.So thanks all for advice and do not buy cheap carb kits on ebay, they’re crap!

Yuza wrote:I would say it is more dull if I understand what you mean. Smoke is black. Choke seems ok, cable moves fine, but it is a good point to control. Any suggestion about how to check it?

Sharp sound could be too lean mixture and dull/ slow could be to rich mixture. And black smoke means too much fuel for sure.Assuming that the cause of the problems is in your carbs, you're engine seems to die because of a too rich mixture.

Too rich mixture can be caused in idle circuit or main circuit.Main circuit is the combination of idle rpm screw (not the problem), float level (checked), float valve (renewed), main air jet and main fuel jet (both not changed). And emulsion tube + needle but these are changed neither. Idle circuit consists of idle air jet, and idle fuel jet and idle mixture screw (IMS). I asume the first two are unchanged. The last option I should check is the IMS. Especially because the problem occurs during idling.

Both carb bodies have an IMS. From factory, the IMS in the right body is capped. I guess you renewed the O-ring from the left IMS. I can imagine that the left IMS is still completely turned in after rebuild. This screw must be turned out about 1,5 turn. Otherwise the idle mixture from the left carb exist of fuel only.

And I've had a few sets of carbs wereby the point of the idle mixture screw was broken and was stuck in the body. You can check this by removing the carbs and IMS, by using a flashlight shining from the cilinder side. Through the hole for the IMS, you should see the light.....

And push back the choke by hand, directly on the carb body to be sure it's closed fully. If necessary, add an extra tension spring to keep it closed.

sounds like you have some issues with fuel overflow. that ~minute or so is just enough to fill the floats with fuel and it dies. wet test may be lying to you, cause when the engine is running, there is vibration everywhere. my big had issues with the float needle valves not having proper spring tension (the tiny pimple had different resistances between the carbs). but seeing as you have got the set from hessler - im running out of ideas

this may seem obvious, but double-check the carb connections: make sure you did not switch carb breather hose with the fuel pump hose.also - double check the fuel pump. suck on the vacuum line to see if you get any fuel in your mouth and last but not least - make sure that the fuel enrichment circle actually disengages when you disengage it. I recall someone had issues with it when it would get stuck half way in the carbs.

So, brought it to the workshop today (friend of mine, bmw mechanic)At idle it seems now ok, so float valves and float needle should work fineAs soon as the throttle is opened few degrees it starts smoking, popping etc, closing the throttle makes it runs fine againChoke works ok also (tested)Note: carbs were cleaned but nothing was changed in the regulations or jet sizes (just installed a new idel jet) and bike was running absolutely fine before...I am now thinking of the main needle, might be worn....But again, it worked before...maybe the oring in the slider guide? Ultrasonic cleaning might have moved it or damaged it...?He will find the cause anyway sooner or later...!